The present invention relates generally to data transmission systems, and more particularly relates to a data framer that is capable of automatically supporting two or more data framing protocols.
It is well known that data communication protocols, for transferring information between a source and a destination over a communication network, typically employ a framing architecture for synchronizing data between the source and destination. A data frame may be divided into various sections, including a message section and an information section (e.g., framing data) associated with the message section which is used, for example, to identify the frame boundaries and maintain the communication network path. The information section typically resides in a header and/or a trailer portion of the data frame. Different data communication protocols often utilize different frame organizations for sending data over the communication network.
A data framer is a device which generally functions in a data link layer of a data transmission system. When utilized at the receiver side of the system, the framer searches an incoming data stream for a data frame of a preset format or protocol. Once the frame boundaries have been identified using the preset protocol, valid user data is located within the frame by subsequent processing stages. On the transmit side, the framer organizes the user data into a frame corresponding to the preset protocol for transmission over the communication network.
Conventional framers are generally capable of processing only a single framing protocol. Since the conventional framer conducts all functions specifically for a selected protocol, received data streams that do not match the selected protocol will not be identified as valid. Likewise, transmitted data streams will only be framed in accordance with the single selected protocol. Additionally, there often exist variants of a given protocol for different data transmission rates. Framers are typically optimized for a targeted data rate. Thus, when the data rate changes, the framer settings must typically be manually modified to correspond to the selected protocol at the desired data rate.
It would be advantageous, therefore, to provide a framer that is capable of automatically supporting multiple framing protocols and/or data transmission rates.
The present invention provides techniques for forming a multi-protocol framer for use, for example, in a data transmission system. The multi-protocol framer is capable of automatically detecting a particular data transfer protocol in an input data stream received from a transmission medium, such as, for example, a fiber optic network. Once the particular protocol has been detected by the framer, the framer is configured to extract valid data from the input data stream and/or frame valid data for transfer over the transmission medium according to the detected protocol. Thus, using the techniques of the present invention, a data framer may be provided that is not only capable of automatically handling multiple data transfer protocols, but eliminates the need for knowing the protocol type a priori.
In accordance with one aspect of the invention, a data framer capable of supporting at least two different data framing protocols potentially present in a source data stream includes two or more framing circuits and a controller coupled to the framing circuits. Each of the framing circuits is configured to extract user data from the source data stream in accordance with a different data framing protocol associated with the respective framing circuit. The controller is operative to: (i) receive the source data stream and automatically determine which of the at least two different data framing protocols corresponds to the source data stream; and (ii) route the source data stream to one of the first framing circuit and the second framing circuit in response to a match between the determined data framing protocol of the source data stream and one of the first and second data framing protocols.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments thereof, which is to be read in connection with the accompanying drawings.